Terahertz (THz) waves generally refer to electromagnetic waves having frequencies ranged from 0.1 to 10 THz. From a view of frequency, THz waves are located between radio waves and light waves, or between millimeter waves and infrared waves, that is, the frequency of THz waves is higher than that of microwaves and is below than that of infrared waves. From a view of energy, the energy of THz waves is between the energy of electrons and the energy of photons. Techniques relating to infrared and microwave, which are distributed on both sides of the THz band in the electromagnetic spectrum, are mature techniques, but techniques on THz is still a blank field for the reason that neither optical theory nor microwave theory is completely suitable for the band of THz. THz systems have a wide range of applications in many fields, such as semiconductor materials, property study of high temperature superconducting materials, tomography technology, unmarked genetic testing, cell-level imaging, chemical and biological inspection, broadband communications, microwave orientation and the like. The study of radiation sources in this band will not only promote the development of the theorical researches, but also present a major challenge to solid-state electronics and circuit technology. It is expected that THz technology will be one of the major emerging science and technology fields in the 21st century.
Currently, conventional electromagnetic fields with lower magnetic field intensities are mainly adopted as magnetic fields of THz sources. There is a need in the art for a more movable and lighter strong-magnetic field focusing system to meet the needs of the usage of high-power THz sources. Also, since the strong-magnetic focusing magnet system utilized in high-power THz sources has a complex magnetic field shape and a higher requirement for the precision of the magnetic field, an improved coil structure is required to achieve the magnetic field intensity and special spatial configuration of the magnetic field required by a high-power THz system. Conventional strong-magnetic focusing magnet systems used for traditional high-power THz sources provide a lower magnetic field intensity, poor field stability, and unsatisfied field precision.